This invention relates to a process for breaking emulsions containing water and oil, preferably aqueous crude oil emulsions.
In the production of crude oils, an increasing amount of water is brought up with the oil as exploitation of the occurrence progresses. Surface-active substances (for example asphaltenes and resins) present in the crude oils emulsify most of the water to form highly stable water-in-oil emulsions. The emulsified water can make up from 0.1 to 90% by weight of the emulsion as a whole. The emulsion water can contain dissolved salts which lead to corrosion problems in the processing of the crude oil or which--as catalyst poisons--can complicate subsequent processing. In addition, the water present in the crude oil leads to increased transportation costs.
Crude oils differ distinctly in their composition according to their origin. In addition, some of the natural emulsifiers present in the crude oils have a complex chemical composition so that specially selected emulsion breakers or demulsifiers have to be used.
The demulsifiers used for aqueous crude oil emulsions are selected from a wide range of different compounds used either individually or in the form of mixtures, for example polyamides, alkylarylsulfonates and phenolic resins (Kim, Y. H., Wasan, D. T., Ind. Eng. Chem. Res. 1996, 35, 1141-1149). DE 44 18 800 A1 claims the use of mixtures of known demulsifiers with polyalkylene glycol ethers for removing water from crude oil. EP 751 203 A2 proposes polymers obtained by reacting certain alkoxylated polyols with aromatic compounds containing reactive groups as demulsifiers. U.S. Pat. No. 3,928,194 describes a number of different classes of compounds as demulsifiers for aqueous crude oil emulsions, including for example glycol esters, fatty acids, fatty add esters, amines, phenolic resins and alkoxylated derivatives thereof.
However, known demulsifiers or mixtures of known demulsifiers are not always satisfactory because separation of the water and oil phases either takes too long or involves an excessive dosage of the demulsifier. In addition, in view of the widely differing composition of crude oils, there is a constant need for improved demulsifiers or demulsifiers adapted to special crude oil qualities.
Accordingly, the problem addressed by the present invention was to provide improved demulsifiers for breaking water-in-oil emulsions which would be suitable in particular for breaking aqueous crude oil emulsions.
It has been found that emulsions containing water and oil can be effectively broken if selected alkoxylation products of carboxylic acid esters are added as demulsifiers to the emulsions.